Battered by criticism, H. David Nahai resigns from DWP

"Fundamental change at the DWP has proven far more difficult than we imagined," said Rhonda Mills, Southern California director of the Clean Power Campaign. "If the mayor's promises are going to be kept, he and his leadership team have to focus on crucial action items like building new renewable transmission lines and a clean-energy portfolio."

Villaraigosa thanked Nahai in writing. Deputy Mayor Janelle Erickson said the resignation does not mean that the mayor will ease up on his push for renewable energy.

"Mayor Villaraigosa is 100% committed to turning the Department of Water and Power into the greenest utility in the country," she said.